Thousands of fish have been killed after chemicals were dumped in the Tolka River.

The tragic scene was discovered yesterday after the river was covered in a bubble bath-like foam.

Dublin City Council and Inland Fisheries Ireland have launched an investigation into the source of the contaminating material that caused the incident.

Brian Beckett of Inland Fisheries Ireland said that thousands of fish had been killed by the pollution.

He said the body had an environmental team on the site from early yesterday after receiving a tip off through their environmental helpline - 1890 34 24 74.

He said they "followed the foam" up the river to an area around the Finglas Road Bridge but added: "We have to be careful to protect the integrity of the case as it is an ongoing investigation.

"We took water samples, but it can be difficult to pin point the source if the source has already gone."

Mr Beckett said it someone had polluted the river by mistake, it would "be a very good idea" for them to come forward

The suds covered a 2km stretch of the Northside river, from the Finglas Road Bridge to Griffith Park .

Fine Gael Councillor Noel Rock has urged that those responsible are held accountable.

Cllr. Rock said: “I have submitted a complaint to the Environmental Protection Agency (EPA) and hope to receive a swift response to the issue, along with a full investigation into the issue.

“I can’t understand why anybody would do this, and I’ve never seen anything like it along this stretch.”

He added that he was especially saddened as Dublin City Council and volunteers have cleaned the weather over the last number of years and he felt “real progress was measured.”

Green Party Councillor Ciarán Cuffe also called on the EPA to investigate, he said: “Earlier this year we were celebrating the return of spawning salmon to the river after a one hundred year absence.

“It would be shameful if this incident destroys the painstaking work that has been undertaken to clean up the river.”

Grace Lambert was shocked to see the fish massacre while she was walking her dog.

Ms Lambert said: “I noticed some foam in the water and thought nothing of it. As I continued along the banks I came across a fisherman packing up his belongs. He pointed out the dead fish suspended in the water, literally hundreds of them, big and small.

“The foam was really bad where the water is flowing fast. Any birds that live along the river look very lethargic and sick. The foam was attracting playing children into the water.”

When contacted, a spokeswoman for the EPA said that the incident does not fall under their responsibilities.

She said: “We may be getting involved, we are currently liaising with the Inland Fisheries board. It is too soon to say if we will be involved in the clean-up efforts.”